This invention relates to a chassis auxiliary-frame arrangement on a preferably self-supporting vehicle body for improving the safety in a crash.
Modern vehicle bodies are equipped in the region of the front wheel suspension with a very stiff chassis auxiliary frame, which improves the absorption of transverse forces and therefore the track stability of the vehicle. In addition, in this construction, during the assembly of the vehicle the complete drive train including the front wheel suspension can be fitted, in an advantageous manner in terms of production, as a complete assembly module into the vehicle body.
However, problems arise from this construction with regard to the safety of the vehicle occupants in a crash. The prior art has therefore disclosed, for the protection of the occupants, in particular in a frontal impact of the vehicle, a multiplicity of measures in which plastic deformation of body parts results in the kinetic energy of the vehicle being converted into deformation energy and the intention is thus to prevent the occupants from accelerating too severely. However, if a chassis auxiliary-frame is fitted, the stiffness of the latter, which is actually desirable in order to improve the track stability, prevents the deformation zones of the body (for example the longitudinal members) from being able to be adequately deformed in the region of the auxiliary frame. In addition, there is the risk that, in a very severe impact, the auxiliary-frame or parts of it will be pressed into the passenger cell, and an additional risk of injuries therefore arises.
U.S. Pat. No. 5,884,963 discloses a body structural element which, in a frontal impact of the vehicle, firstly absorbs kinetic energy, by means of its specific deformation, and, secondly, directs a chassis auxiliary frame under the passenger cell as the deformation continues. Although the auxiliary-frame is therefore prevented from penetrating the passenger cell, the disadvantage of this invention is that the deformation zones of the body cannot be adequately and uniformly deformed in the region of the auxiliary frame on account of the rigidity thereof.
Therefore also in the energy conversion method disclosed in U.S. Pat. No. 6,367,869, the chassis auxiliary-frame remains in the region of the deformation zones of the body after a frontal impact and thus prevents their adequate and uniform deformation. Only the rear part of the auxiliary frame is detached here from the body by means of a deformable auxiliary fastening plate in order thereby to prevent the auxiliary frame from penetrating the passenger cell.
U.S. Pat. No. 6,109,654 discloses a shock-absorbing vehicle structure in which rear fastenings of a chassis auxiliary frame become detached one after another in a specifically defined manner resulting in the deformation of the left and right body and auxiliary-frame parts. It discloses that the result of the overall acceleration/deceleration peaks or values experienced by the vehicle occupants are lessened when the resultant acceleration peaks are experienced successively. However, this does not alter the fact that here too the relatively stiff auxiliary-frame parts remain in the region of the deformation zones of the body and therefore prevent their adequate and uniform deformation.